CN117941277A

CN117941277A - Phase compensation for channel state information

Info

Publication number: CN117941277A
Application number: CN202180101961.XA
Authority: CN
Inventors: 王文剑
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2024-04-26
Also published as: WO2023028797A1

Abstract

Embodiments of the present disclosure relate to apparatuses, methods, devices, and computer-readable storage media for PHE compensation of CSI. The method comprises the following steps: determining a first estimate of the composite channel when a plurality of first sensing signals are received via a first set of antennas within a time window, the first sensing signals being received from a second device via a second set of antennas and reflected by at least one object in the composite channel; determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatch for a plurality of antenna pairs, the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from a first set of antennas and a transmit antenna from a second set of antennas; determining compensation information for the composite channel based on the phase error information; determining a second estimate for the composite channel based on the compensation information and the first estimate; and transmitting CSI of the composite channel to the second device based on the second estimate and the first sensing signal.

Description

Phase compensation for channel state information

Technical Field

Embodiments of the present disclosure relate generally to the field of telecommunications and, in particular, relate to an apparatus, method, device, and computer-readable storage medium for phase compensation of Channel State Information (CSI).

Background

Interest in the combined communication and sensing system (JCAS) is growing. In JCAS systems, JCAS devices (such as base stations and user equipment) can communicate with each other and simultaneously sense the environment to determine the location and speed of nearby objects. Various emerging applications rely on accurate measurement of CSI obtained from JCAS devices. The time series of CSI measurements reflects how wireless signals propagate through surrounding objects and humans in the time, frequency and spatial domains and thus can be used for various wireless sensing applications. For example, CSI amplitude variations in the time domain have different patterns for different people, activities, gestures, etc., and can be used for human presence detection, fall detection, motion detection, activity recognition, gesture recognition, and identification/authentication of people. CSI phase shifts in the spatial and frequency domains (i.e., transmit/receive antennas and carrier frequencies) are related to signal transmission delays and directions, which can be used for human localization and tracking. The CSI phase offset in the time domain may have different dominant frequency components, which may be used for the estimation of the human respiratory frequency.

Disclosure of Invention

Example embodiments of the present disclosure provide solutions for phase compensation of CSI.

In a first aspect, an apparatus is provided. The apparatus includes at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, determining a first estimate of a composite channel between the device and a second device, the plurality of first sensing signals being received from the second device via a second set of antennas and reflected by at least one object in the composite channel; determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs in the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from a first set of antennas and a transmit antenna from a second set of antennas; determining compensation information for the composite channel based on the phase error information; determining a second estimate for the composite channel based on the compensation information and the first estimate; and transmitting channel state information of the composite channel to the second device based on the second estimate and the plurality of first sensing signals.

In a second aspect, a second device is provided. The second device includes at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the second device to at least: transmitting, via the second set of antennas, a plurality of first sensing signals to a first device having the first set of antennas within a time window, the plurality of first sensing signals reflected by at least one object in the composite channel; receiving channel state information of a composite channel from a first device, the channel state information being determined based on a plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from a first set of antennas and a transmitting antenna from a second set of antennas; determining a signal pattern based on the channel state information; and in another time window later than the time window, transmitting a second sensing signal to the first device based on the signal pattern.

In a third aspect, a method is provided. The method comprises the following steps: at the device, in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, determining a first estimate of a composite channel between the device and a second device, the plurality of first sensing signals being received from the second device via a second set of antennas and reflected by at least one object in the composite channel; determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs in the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from a first set of antennas and a transmit antenna from a second set of antennas; determining compensation information for the composite channel based on the phase error information; determining a second estimate for the composite channel based on the compensation information and the first estimate; and transmitting channel state information of the composite channel to the second device based on the second estimate and the plurality of first sensing signals.

In a fourth aspect, a method is provided. The method comprises the following steps: transmitting, at the second device, a plurality of first sensing signals via the second set of antennas within the time window to a first device having the first set of antennas, the plurality of first sensing signals reflected by at least one object in the composite channel; receiving channel state information of a composite channel from a first device, the channel state information being determined based on a plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from a first set of antennas and a transmitting antenna from a second set of antennas; determining a signal pattern based on the channel state information; and in another time window later than the time window, transmitting a second sensing signal to the first device based on the signal pattern.

In a fifth aspect, there is provided an apparatus comprising: means for determining a first estimate of a composite channel between the apparatus and a second apparatus in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, the plurality of first sensing signals being received from the second apparatus via a second set of antennas and reflected by at least one object in the composite channel; means for determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs in the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from a first set of antennas and a transmit antenna from a second set of antennas; means for determining compensation information for the composite channel based on the phase error information; means for determining a second estimate for the composite channel based on the compensation information and the first estimate; and means for transmitting channel state information of the composite channel to the second apparatus based on the second estimate and the plurality of first sensing signals.

In a sixth aspect, there is provided an apparatus comprising: means for transmitting a plurality of first sensing signals to a first device having a first set of antennas via a second set of antennas within a time window, the plurality of first sensing signals being reflected by at least one object in a composite channel; means for receiving channel state information of a composite channel from a first apparatus, the channel state information being determined based on a plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from a first set of antennas and a transmitting antenna from a second set of antennas; means for determining a signal pattern based on the channel state information; and means for transmitting the second sensing signal to the first device based on the signal pattern in another time window that is later than the time window.

In a seventh aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the third aspect.

In an eighth aspect, there is provided a computer readable medium having a computer program stored thereon, which when executed by at least one processor of a device, causes the device to perform the method according to the fourth aspect.

Other features and advantages of embodiments of the present disclosure will be apparent from the following description of the particular embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the embodiments of the disclosure.

Drawings

Embodiments of the present disclosure are presented in an exemplary sense and their advantages are explained in more detail below with reference to the drawings, wherein:

FIG. 1 illustrates an example network environment in which example embodiments of the present disclosure may be implemented;

Fig. 2 shows a signaling diagram illustrating a process for PHE compensation of CSI according to some example embodiments of the present disclosure;

3A-3D illustrate schematic diagrams of performance evaluations with PHN-free idealities, PHN-free and PHN-free compensations legacy cases, and PHN-and PHE-compensated cases in various field measurement scenarios, according to some example embodiments of the present disclosure;

fig. 4 illustrates a flowchart of an example method for PHE compensation of CSI according to some embodiments of the present disclosure;

fig. 5 illustrates a flowchart of an example method for PHE compensation of CSI according to some embodiments of the present disclosure;

FIG. 6 illustrates a simplified block diagram of a device suitable for implementing exemplary embodiments of the present disclosure; and

Fig. 7 illustrates a block diagram of an example computer-readable medium, according to some embodiments of the disclosure.

The same or similar reference numbers will be used throughout the drawings to refer to the same or like elements.

Detailed Description

Principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described merely for the purpose of illustrating and helping those skilled in the art understand and practice the present disclosure and are not meant to limit the scope of the present disclosure in any way. The disclosure described herein may be implemented in various ways other than those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

References in the present disclosure to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It will be understood that, although the terms "first" and "second" may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish between functions of the various elements. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," "including," "having," "has," "containing," and/or "having," when used herein, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.

As used herein, the term "circuitry" may refer to one or more or all of the following:

(a) A pure hardware circuit implementation (such as an implementation using only analog and/or digital circuitry), and

(B) A combination of hardware circuitry and software, such as (as applicable):

(i) Combination of analog and/or digital hardware circuit(s) and software/firmware, and

(Ii) Any portion of the hardware processor(s) (including digital signal processors), software, and memory(s) with software that work together to cause a device (such as a mobile phone or server) to perform various functions, and

(C) Hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), that require software (e.g., firmware) to operate, but software may not be present when operation is not required.

The definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this disclosure, the term circuitry also encompasses implementations of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. For example, if applicable to the particular claim elements, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as a fifth generation (5G) system, long Term Evolution (LTE), LTE-advanced (LTE-a), wideband Code Division Multiple Access (WCDMA), high Speed Packet Access (HSPA), narrowband internet of things (NB-IoT), wi-Fi, and the like. Furthermore, communication between a terminal device and a network device in a communication network may be performed according to any suitable generation of communication protocols, including, but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) New Radio (NR) communication protocols, and/or any other protocols currently known or developed in the future. Embodiments of the present disclosure may be applied in various communication systems. In view of the rapid development of communications, there will of course also be future types of communication technologies and systems that can implement the present disclosure. And should not be taken as limiting the scope of the present disclosure to only the above-described systems.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. A network device may refer to a Base Station (BS) or an Access Point (AP), such as a node B (NodeB or NB), an evolved node B (eNodeB or eNB), a NR next generation node B (gNB), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a relay, a low power node (such as femto, pico), etc., depending on the terminology and technology applied. The RAN split architecture includes a gNB-CU (centralized unit, hosting RRC, SDAP, and PDCP) controlling multiple gNB-DUs (distributed unit, hosting RLC, MAC, and PHY). The relay node may correspond to the DU portion of the IAB node.

The term "terminal device" refers to any terminal device capable of communication. By way of example, and not limitation, a terminal device may also be referred to as a communication device, a User Equipment (UE), a Subscriber Station (SS), a portable subscriber station, a Mobile Station (MS), or an Access Terminal (AT). The terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable terminal devices, personal Digital Assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, notebook computer embedded devices (LEEs), notebook computer mounted devices (LMEs), USB dongles, smart devices, wireless client devices (CPE), internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in an industrial and/or automated processing chain environment), consumer electronic devices, devices operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Terminal (MT) part of an Integrated Access and Backhaul (IAB) node (also referred to as a relay node). In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

Although in various exemplary embodiments, the functions described herein may be performed in fixed and/or wireless network nodes, in other exemplary embodiments, the functions may be implemented in a user equipment device (such as a cell phone or tablet or notebook or desktop or mobile IoT device or fixed IoT device). For example, the user equipment device may be equipped with the respective functions described in connection with the fixed and/or radio network node(s). The user equipment device may be a user equipment and/or a control device, such as a chipset or processor, configured to control the user equipment when the user equipment is installed therein. Examples of such functions include a bootstrapping server function and/or a home subscriber server, which may be implemented in a user equipment device by providing the user equipment device with software configured to cause the user equipment device to execute from the perspective of these functions/nodes.

Integrated JCAS or 5G NR systems have attracted considerable attention because of their advantages in reducing system size, weight and power consumption, reducing electromagnetic interference, and various application scenarios. Different sensing applications have different requirements on signal processing techniques and classification/estimation algorithms. Some sources of CSI measurement error can be summarized as follows:

1) Power Amplifier Uncertainty (PAU), which may be due to resolution limitations of hardware. For example, atheros 9380 is 0.5db, the total gain achieved by the lna and PGA may not fully compensate for the signal amplitude fading to the transmit power level; the measured CSI amplitude is equal to the compensated power level, mixed with power amplifier uncertainty error, resulting in CSI amplitude offset;

2) I/Q imbalance may cause quadrature baseband signals to be corrupted when amplitude and phase distortions occur; once the I/Q imbalance, after sampling and FFT, the result will be distorted CSI;

3) Carrier Frequency Offset (CFO): the center frequencies of the transmission pairs may not be completely synchronized; the carrier frequency offset is compensated by the CFO corrector of the receiver, but due to the imperfect hardware, the compensation may be incomplete and the signal still carries the residual CFO, resulting in a CSI phase offset on the sub-carriers that varies with time;

4) Sampling Frequency Offset (SFO): because clocks are not synchronous, sampling frequencies of a transmitter and a receiver can deviate, and time deviation of a receiving signal converted by an ADC relative to a transmitting signal can be caused; residual SFO can cause spin errors after the SFO corrector; since the clock skew is relatively stable for a short period of time (e.g., a few minutes [10 ]), this phase rotation error is almost constant;

5) Packet Detection Delay (PDD), resulting from energy detection or correlation detection in digital processing after down-conversion and ADC sampling; packet detection introduces another time-shifted phase rotation error;

6) PLL Phase Offset (PPO) responsible for generating the center frequencies of the transmitter and receiver starting from a random initial phase; thus, CSI phase measurements of the receiver may be disturbed by the additional phase offset;

7) Phase Ambiguity (PA): when checking the phase difference between two receiving antennas, recent work verifies that there is a so-called four-way phase ambiguity when operating at 2.4 GHz.

Deriving accurate channel frequency response from CSI measurements has been a challenging task due to the hardware imperfections of JCAS devices. Non-negligible linear and non-linear CSI phase errors (PHEs) are common among various wireless devices or JCAS devices. For example, for JCAS systems using orthogonal frequency division multiplexing multiple input multiple output (OFDM-MIMO), CSI may be considered as a complex-valued matrix representing multipath channel amplitude fading and phase shifting, whereas JCAS systems using OFDM-MIMO are likely to be affected by such PHEs, resulting in inaccurate measurements of CSI. This is because when a large number of antennas are operated in a high frequency band, the quadrature multi-frequency system is more sensitive to synchronization errors than a single carrier system, and Radio Frequency (RF) distortion in the high frequency band is much more severe than in a conventional low frequency band, the PHE itself appears as a random time-varying phase difference between oscillators connected to the BS and UE antennas, resulting in inter-carrier interference (ICI) and signal constellation rotation. Thus, the PHE may generate Common Phase Error (CPE) and ICI at the receiver, thereby degrading the performance of the network system.

Inaccurate CSI may adversely affect subsequent signals from the sender device to the receiver device in JCAS and have a significant impact on the performance of JCAS. Thus, for either the 5GNR or JCAS system, timing offset estimation, PHE estimation, tracking, and compensation are always needed, which requires improved channel estimation and CSI feedback in JCAS. Some phase noise (PHN) compensation schemes have been proposed to mitigate the effect of PHN on system performance. However, these schemes consider theoretical models rather than engineering and therefore have relatively high complexity or complex algorithms.

Given that hardware impairments can greatly impact CSI quality, and that the I/Q imbalance used in the transceiver, SFO, PDD, PPO, and the PHN introduced by the noise local oscillator are the main causes of this problem, embodiments of the present disclosure provide an enhanced PHE compensation scheme. By compensating the PHN during channel estimation, this scheme may provide accuracy of CSI measurement with low complexity. This also helps the transmitter of the sense signal adjust the signal pattern for JCAS systems, thereby optimizing the subsequent sense signal. In this way, system performance may be improved while power consumption of JCAS devices may be reduced.

Fig. 1 illustrates an example network environment 100 in which example embodiments of the present disclosure may be implemented. The network environment 100 may be a JCAS system or any other network system. As shown in fig. 1, the example environment 100 may include a plurality of devices including first devices 110-1 through 110-J (hereinafter may also be referred to as UEs 110-1 through 110-J/first devices 110-1 through 110-J, or collectively UE 110/first device 110) and second devices 120 serving the first devices 110-1 through 110-J. The example environment 100 may also include at least one object, such as an object 130 located between the first devices 110-1 through 110-J and the second device 120 over a multipath channel. In the context of the present disclosure, a multipath channel may also be referred to as a composite channel.

By way of example, the example environment 100 is a JCAS MIMO system, e.g., JCAS system with millimeter wave massive MIMO. In environment 100, first device 110 and second device 120 perform point-to-point (P2P) communication and concurrently sense the environment to determine parameters or characteristics of nearby objects (e.g., object 130), including but not limited to location, speed, gestures, activity, identities of nearby objects, and the like. The link from the second device 120 to the first device 110 is referred to as the Downlink (DL), and the link from the first device 110 to the second device 120 is referred to as the Uplink (UL). In DL, the second device 120 is a Transmitting (TX) device or transmitter, and the first device 110 is a Receiving (RX) device or receiver. In the UL, the first device 110 is a TX device or transmitter and the second device 120 is an RX device or receiver.

In the following description, DL transmission of a sensing signal is given in a schematic manner. Assume that a first device 110 (which may be any one of first devices 110-1 through 110-J) has N receive antennas and a second device 120 has M transmit antennas. Thus, there are a total of mxn pairs of transmit and receive antennas, and the first device 110 and the second device communicate packets or signals through the mxn antenna array.

The second device 120 may directly transmit a packet or signal for communication with the first device 110. In addition, the second device 120 may also transmit packets or signals for sensing. As shown in fig. 1, a signal transmitted from the second device 120 may propagate along a multipath channel between the first device 110 and the second device 120. Upon encountering the object 130, the sensing signal will be reflected by the object 130 and then reach and be received by the first device 110.

The packets transmitted by the second device 120 may include a data payload and pilot signals for synchronization and channel estimation. The pilot signal has various forms including comb pilot, block pilot, trellis pilot, etc. Without loss of generality, in the context of embodiments of the present disclosure, a general data structure includes a training symbol sequence, denoted by L _t, and data symbols, denoted by L _d, for each spatial stream. Thus, the total length of the sensing signal is denoted by l=l _t+L_d. By concatenating symbols from the M spatial streams into a matrix X, the signal transmitted from the second device 120 to the first device 110 may be represented by x= [ X _t,X_d, whereAndWhere X _t (m) and X _d (m) represent pilot and data symbols, respectively, transmitted from the mth antenna.

In practice, assuming a frequency-flat rayleigh fading channel between the first device 110 and the second device 120, each transmit and receive antenna may be equipped with an independent oscillator, meaning that the local oscillators for the transmit or receive antennas may be different, resulting in different PHNs. The first device 110 measures and analyzes the signals for sensing and estimates the composite channel between the first device 110 and the second device 120.

In an example embodiment, the first device 110 may determine PHN compensation information of the composite channel in an antenna pair wise manner and estimate the composite channel based on the PHN compensation information and thus the channel estimation is more accurate.

In an example embodiment, the first device 110 may generate CSI for the composite channel based on the channel estimate and transmit the CSI to the second device 120. Upon receiving the CSI, the second device 120 may adjust the signal pattern used for sensing to maximize Mutual Information (MI) between the composite channel and the reflected signal from the object to be sensed by the first device 110.

It should be understood that the number of first devices, second devices, and objects are given for illustrative purposes only and do not imply any limitation to the present disclosure. Network system 100 may include any suitable number of devices and/or objects suitable for implementing implementations of the present disclosure, and the composite channel between the first device and the second device may be more complex or simple. Although not shown, it is to be appreciated that one or more additional devices can be located in the environment 100.

It should also be understood that although illustrated as a terminal device, the first device may be other devices than a terminal device. Further, although illustrated as a base station, the second device may be a network device or a portion of a network device other than a base station, e.g., at least a portion of a terrestrial network device or a non-terrestrial network device.

Depending on the communication technology, network system 100 may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a single carrier frequency division multiple access (SC-FDMA) network, or any other type of network. The communications discussed in network 100 may conform to any suitable standard including, but not limited to, new radio access (NR), long Term Evolution (LTE), LTE evolution, LTE-advanced (LTE-a), wideband Code Division Multiple Access (WCDMA), code Division Multiple Access (CDMA), CDMA2000, global system for mobile communications (GSM), and the like. In addition, the communication may be performed according to any generation communication protocol now known or later developed. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols. The techniques described below may be used for the radio networks and radio technologies described above as well as other radio networks and radio technologies. For clarity, certain aspects of the technology will be described below in the description for NR and JCAS.

The principles and implementations of the present disclosure are described in detail below with reference to fig. 2 through 5. Fig. 2 shows a signaling diagram illustrating a process 200 for PHE compensation of CSI according to some example embodiments of the present disclosure. For discussion purposes, process 200 will be described with reference to FIG. 1. Process 200 may involve first device 100, second device 120, and object 130.

In process 200, the second device 120 transmits 205 a plurality of first sensing signals via the second set of antennas within a time window. The time window may include a plurality of subframes. In the example shown in fig. 1-2, the second set of antennas includes M transmit antennas.

As described above, the first sensing signal propagates on the composite channel and is reflected by the object 130 and is then received by the first device 110 via the first set of antennas. In the example shown in fig. 1-2, the first set of antennas includes N receive antennas. For the jth first device 110-j, where j e [1, j ], the first sensing signal reflected from the object 130 may be described as follows:

Where K _jl＝diag{{β_j1β_j2Lβ_jl represents the large scale fading coefficients between the first device 110-j and the second device 120, H _j represents a preconfigured channel function, which may be in the form of a channel matrix, Φ _R represents the PHN matrix of the first device 110-j, and Φ _T represents the PHN matrix of the second device 120, ICI represents subcarrier interference and v _j represents additive white gaussian noise. The expression Φ _RH_jΦ_T may indicate Common Phase Errors (CPEs) caused by PHNs, which are common in actual development, measurement and testing in a massive MIMO engineering verification platform if no compensation scheme is employed.

After receiving the plurality of first sensing signals in the time window, the first device 110-j determines 210 a first estimate of the composite channel. The first estimate of the composite channel may be a PHN corrupted coarse channel estimate introduced by the first device 110-j and the second device 120 (e.g., by their local oscillators). By way of example, the first channel matrix may be determined as follows:

Wherein each matrix element represents an estimated path channel associated with a pair of transmit and receive antennas and the subscripts represent respective indices to the transmit and receive antennas.

Since PHN is time-varying and varies from symbol to symbol, this can be modeled as a Wiener (Wiener) process. Thus, the first and second substrates are bonded together,And/>Not only between symbols, but also between subframes in the time domain. Therefore, it is desirable to reduce the impact of PHN matrices Φ _R and Φ _T.

The first device 110-j determines PHE information based on the first estimate of the composite channel. The PHE information indicates the PHE that caused the respective phase mismatch between the phases associated with the first antenna pair H ₁₁ and the plurality of second antenna pairs, i.e., from H ₁₂ to H _NM.

To determine PHE information, the first device 110-j may first determine the relative phase mismatch coefficient Δφ _i,nm on the i-th subframe in the time window by aligning the respective phase of each element with the phase H ₁₁ of the element. The phase mismatch coefficients ΔΦ _i,nm are combined into a phase mismatch matrix as described below:

Wherein the method comprises the steps of The corresponding phase mismatch coefficient ΔΦ _i,nm for the ith subframe in the time window is represented.

The first device 110-j may then determine the average phase mismatch coefficient ΔΦ _nm based on a time window comprising a plurality of subframes k=0, …, i. The time window may also be referred to as a smooth window. By way of example, if computational complexity is not considered, the first device 110-j may theoretically calculate the angular difference between any two vectors.

Based on the PHE information, the first device 110-j determines 215 compensation information for the composite channel. The compensation information indicates compensation of the PHE and, thus, the PHE may be removed. In some example embodiments, the compensation information may be described as follows in the form of a compensation matrix:

wherein the compensation matrix ψ "can be regarded as the conjugate of each element in the phase mismatch matrix ψ'.

Using the compensation information, the PHNs represented by Φ _R and Φ _T can be removed from the channel estimation. The first device 110-j determines 220 a second estimate of the composite channel based on the compensation information and the first estimate of the composite channel. The second estimate of the composite channel may be considered as an improved channel estimate with PHN compensation for the first device 110-j and the second device 120.

In some example embodiments, the second estimate of the composite channel may be in the form of a second channel matrix. From equations (2) to (4), the second channel matrix can be described as follows:

The first device 110-j generates 225 CSI comprising the compensation information based on the composite second estimate and sends 230 the CSI to the second device 120. By uniquely determining the compensation information based on the reception antennas and the transmission antennas in a pair-wise manner, the accuracy of CSI is significantly improved.

Upon receiving the CSI, the second device 120 adjusts 235 the signal pattern for the sense signal to maximize the MI of the first device 110-j. In some example embodiments, the second device 120 may determine a signal pattern for transmitting the signal X _d in the space-time domain in a matrix form. The signal pattern may be determined to maximize the MI associated with the composite channel. One of the various implementations is given below:

where xi is derived based on the compensating composite channel H "_i,j, Θ is a preconfigured matrix that satisfies Θ ^HΘ＝I_N, Is a right cell matrix after Singular Value Decomposition (SVD) of the composite channel covariance matrix H "_i,jH″_i,j ^H, and Λ=diag ([ lambda _1,1,...,λ_i,i,...,λ_N,N) is a diagonal matrix with singular values of lambda _i,i.

The second device 120 transmits 240 the sensing signal in another time window later than the time window based on the signal pattern determined in 235. The other time window may include at least one subframe.

It should be understood that the formulas, equations, expressions, algorithms, etc. described in process 200 are presented for purposes of illustration and not limitation. The PHE compensation scheme, in particular the compensation information, may be implemented in different forms or by using variations of the above.

Fig. 3A to 3D illustrate schematic diagrams of performance evaluation in various field measurement scenarios without the ideal case of PHN, with the conventional case of PHN and without PHN compensation, and with the enhanced case of PHN and with the application of a PHE compensation scheme (abbreviated as scheme 1), according to some example embodiments of the present disclosure.

The performance evaluations shown in fig. 3A to 3D were obtained based on the simulation parameters shown in the following table.

Table 1 simulation parameters for the PHE compensation scheme

The field measurement scenario includes a line of sight (LOS) outdoor distance of up to 200 meters at a transmit power of 30dBm and a LOS indoor distance of up to 30 meters at a transmit power of 24dBm, supporting NLOS. Specifically, fig. 3A shows performance evaluations for three cases using 64 transmit antennas and 4 receive antennas (e.g., 64Tx4 Rx) at sf= 552.96 MHz. Fig. 3b shows performance evaluation for three cases using 64 transmit antennas and 16 receive antennas (e.g., 64Tx16 Rx) at sf= 552.96 MHz. Fig. 3C shows performance evaluations at sf= 1.10592GHz for three cases using 64 transmit antennas and 4 receive antennas. Fig. 3D shows performance evaluations at sf= 1.10592GHz for three cases using 64 transmit antennas and 16 receive antennas. The evaluation index of the performance gain shown in fig. 3A to 3D is mainly the spectral efficiency, and the total throughput can be determined by multiplying the spectral efficiency by the bandwidth.

As shown in fig. 3A to 3D, the performance gain of scheme 1 is relatively significant when fewer receiving antennas are provided. At medium SNR segments, i.e. signal to noise ratios between 10dB and 20dB, the gain is relatively large and the gap from ideal is also relatively large, which means that the compensation scheme provides effects in these intervals. While at very low and very high SNR segments, i.e. signal to noise ratios below 10dB or exceeding 20dB, the compensation effect is not obvious, which is common for all three cases. As their performance approaches a similar upper performance limit, the compensation effect becomes smaller.

Further, referring to fig. 3B and 3D, illustrating a 64Tx16Rx scenario, the enhanced case provides an average gain of about 22.9% over the conventional case within the SNR segment from 7dB to 20dB by using scheme 1. Referring to fig. 3A and 3C, a scenario of 64Tx4Rx is illustrated, with an average gain of up to 37.4% for the enhanced case relative to the conventional case within a similar SNR segment by using scheme 1. This phenomenon may be due to the receiving antenna.

The evaluation results shown in fig. 3A to 3D indicate that the smoothing process mentioned in the algorithm design plays an important role in these schemes than other algorithm details when more receiving antennas are equipped. On the other hand, when fewer receiving antennas are provided, the performance difference between the three schemes is relatively large, and thus details of the algorithm design may become more important considerations. In summary, when designing the PHE compensation algorithm of a communication system, a trade-off may need to be made between sharing principles and algorithm details, such as smoothing, depending on the system antenna configuration.

It should be appreciated that process 200 may be implemented in whole or in part multiple times, e.g., in an iterative fashion, or over a time interval. By way of example, in the event that the object 130 moves such that its location changes, additionally or alternatively the state of the composite channel changes, the terminal device and the network device may need to again implement the process 200.

In an embodiment of the present disclosure, CSIPHE compensation schemes are provided. According to this scheme, PHE compensation can be achieved with low complexity. After PHE compensation, the accuracy of the CSI can be increased, thereby improving the signal design of the transmitted signal. Thus, the MI between the sensing channel and the reflected signal from the sensing object at the UE can be maximized, thereby improving system performance.

Corresponding to the procedure described in connection with fig. 2, embodiments of the present disclosure provide a solution for enabling PHE compensation of CSI in a terminal device and a network device. These methods will be described below with reference to fig. 4 and 5.

Fig. 4 illustrates a flowchart of an example method 400 for PHE compensation of CSI according to some embodiments of the present disclosure. The method 400 may be implemented at any of the first devices 110-1 through 110-J as shown in fig. 1. For discussion purposes, the method 500 will be described with reference to fig. 1.

At 410, the first device 110 receives a plurality of first sensing signals via a first set of antennas within a time window. The plurality of sensing signals are received from the second device 120 via the second set of antennas and reflected by at least one object 130 in the composite channel between the first device 110 and the second device 120.

At 420, the first device 110 determines a first estimate for the composite channel. In some example embodiments, the first estimate of the composite channel may be corrupted by noise (e.g., PHN) from the first device 110 and the second device 120, and thus contain a PHE.

In some example embodiments, the first estimate of the composite channel may be in the form of a first channel matrix. The first channel matrix may be determined by the first device 110 based on a matrix of composite channels, a first phase noise matrix associated with the first device 110, and a second phase noise matrix associated with the second device 120.

At 430, the first device 110 determines PHE information indicative of antenna pair phase mismatch for the plurality of antenna pairs based on the first estimate. The antenna pairs of the plurality of antenna pairs are different from each other and each antenna pair includes a receive antenna from the first set of antennas and a transmit antenna from the second set of antennas.

In some example embodiments, the antenna pair phase mismatch may be: a phase mismatch between a first phase of the first sense signal associated with a first one of the plurality of antenna pairs and a second phase of the respective first sense signal associated with each of the remaining ones of the plurality of antenna pairs.

In some example embodiments, the phase error information may include a phase error matrix. The first device 110 may determine, for a time window, a set of phase mismatch coefficients indicative of respective phase mismatch between the first antenna pair and each of the remaining antenna pairs from the plurality of antenna pairs. The first device 110 may then determine a phase error matrix based on the set of phase mismatch coefficients.

At 440, the first device 110 determines compensation information for the composite channel based on the phase error information. In some example embodiments, the compensation information may include a compensation matrix indicating antenna pair phase compensation corresponding to the antenna pair phase mismatch.

At 450, the first device 110 determines a second estimate for the composite channel based on the phase compensation information and the first estimate. In some example embodiments, the second estimate of the composite channel may comprise a second channel matrix of the composite channel.

In some example embodiments, the first device 110 may determine the second channel matrix by multiplying elements of the same location in the first channel matrix and the compensation matrix.

At 460, the first device 110 transmits CSI of the composite channel to the second device 120. CSI is determined based on the second estimate and the plurality of first sensing signals.

In some example embodiments, the first device 110 receives the second sensing signal from the second device 120 over another time window that is later than the time. The other time window may include at least one subframe. The second sensing signal is transmitted by the second device 120 based on the signal pattern determined from the CSI.

It should be appreciated that the process 400 may be implemented multiple times at the first device 110, in whole or in part, for example, in an iterative fashion, or within a time interval.

Fig. 5 illustrates a flowchart of an example method 500 for PHE compensation of CSI according to some embodiments of the present disclosure. The method 500 may be implemented at the second device 120 as shown in fig. 1. For discussion purposes, the method 500 will be described with reference to FIG. 1.

At 510, the second device 120 transmits a plurality of first sensing signals to the first device 110 having the first set of antennas via the second set of antennas within a time window. The plurality of first sensing signals are reflected by at least one object in the composite channel.

At 520, the second device 120 receives channel state information of a composite channel from the first device 110, the channel state information of the composite channel being determined based on the plurality of first sensing signals and the compensation information of the composite channel. The compensation information is determined based on antenna pair phase mismatch for the plurality of antenna pairs. The antenna pairs of the plurality of antenna pairs are different from each other and each antenna pair includes a receive antenna from the first set of antennas and a transmit antenna from the second set of antennas.

In some example embodiments, antenna pair phase mismatch indicates: the first phase of the first sense signal associated with a first one of the plurality of antenna pairs and the second phase of the respective first sense signal associated with each of the remaining ones of the plurality of antenna pairs are mismatched, and the compensation information indicates an antenna pair phase compensation corresponding to the antenna pair phase mismatch.

In 530, the second device 120 determines a signal pattern based on the CSI.

In some example embodiments, the second device 120 may adjust the signal pattern to maximize the MI between the composite channel and the reflected signal from the sensing object 130 at the first device 110.

In some example embodiments, the second device 120 determines an estimate of the composite channel based on the CSI. The estimation of the composite channel may be compensated by antenna pair phase compensation corresponding to the antenna pair phase mismatch. The second device 120 may then determine a signal pattern based on the estimate of the composite channel.

In some example embodiments, the second device may generate the second sensing signal at the time-space domain based on the above equation (6).

At 540, the second device 120 transmits a second sensing signal in another time window that is later than the time window based on the determined signal pattern. The other time window may include at least one subframe.

It should be appreciated that the method 500 may be implemented multiple times at the second device 120, for example, in an iterative manner, or within a certain time interval.

In some example embodiments, an apparatus capable of performing the method 400 (e.g., implemented at a UE or any of the first devices 110-1 through 110-J) may include means for performing the respective steps of the method 400. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, the apparatus includes: means for determining a first estimate of a composite channel between the apparatus and a second apparatus in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, the plurality of first sensing signals being received from the second apparatus via a second set of antennas and reflected by at least one object in the composite channel; means for determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs in the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from a first set of antennas and a transmit antenna from a second set of antennas; means for determining compensation information for the composite channel based on the phase error information; means for determining a second estimate for the composite channel based on the compensation information and the first estimate; and means for transmitting channel state information of the composite channel to the second apparatus based on the second estimate and the plurality of first sensing signals.

In some example embodiments, the first estimate comprises a phase error caused by the apparatus and the second apparatus, and the antenna pair phase mismatch comprises: a phase mismatch between a first phase of the first sense signal associated with a first one of the plurality of antenna pairs and a second phase of the respective first sense signal associated with each of the remaining ones of the plurality of antenna pairs.

In some example embodiments, the phase error information comprises a phase error matrix, and the means for determining the phase error information comprises: means for determining a set of phase mismatch coefficients for the time window, the set of phase mismatch coefficients being indicative of a respective phase mismatch between a first antenna pair and each of the remaining antenna pairs from the plurality of antenna pairs; and means for determining a phase error matrix based on the set of phase mismatch coefficients.

In some example embodiments, the first estimate for the composite channel includes a first channel matrix determined based on a matrix of the composite channel, a first phase noise matrix associated with the apparatus, and a second phase noise matrix associated with the second apparatus.

In some example embodiments, the compensation information includes a compensation matrix indicating antenna pair phase compensation corresponding to an antenna pair phase mismatch.

In some example embodiments, the first estimate for the composite channel comprises a first channel matrix for the composite channel and the second estimate for the composite channel comprises a second channel matrix for the composite channel, the means for determining the second estimate comprises: the second channel matrix is determined by multiplying the elements of the same position in the first channel matrix and the compensation matrix.

In some example embodiments, the apparatus further comprises: means for receiving a second sensing signal from the second device in another time window that is later than the time window, the second sensing signal being received from the second device based on a signal pattern determined from the channel state information.

In some example embodiments, the apparatus is a terminal device and the second apparatus is a network device.

In some example embodiments, an apparatus capable of performing the method 500 (e.g., implemented at the gNB or the second device 120) may include means for performing the respective steps of the method 500. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some embodiments, an apparatus comprises: means for transmitting a plurality of first sensing signals to a first device having a first set of antennas via a second set of antennas within a time window, the plurality of first sensing signals being reflected by at least one object in a composite channel; means for receiving channel state information of a composite channel from a first apparatus, the channel state information being determined based on a plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from a first set of antennas and a transmitting antenna from a second set of antennas; means for determining a signal pattern based on the channel state information; and means for transmitting the second sensing signal to the first device based on the signal pattern in another time window that is later than the time window.

In some example embodiments, the means for determining the signal pattern comprises: means for determining an estimate for the composite channel based on the CSI, the estimate for the composite channel being compensated by an antenna pair phase compensation corresponding to the antenna pair phase mismatch; and means for determining a signal pattern based on the estimate of the composite channel such that mutual information associated with the composite channel is maximized.

In some example embodiments, the first apparatus is a terminal device and the apparatus is a network device.

Fig. 6 is a simplified block diagram of a device 600 suitable for implementing embodiments of the present disclosure. Device 600 may be provided to implement a communication device, such as first devices 110-1 through 110-J and second device 120 as shown in fig. 1. As shown, device 600 includes one or more processors 610, one or more memories 620 coupled to processors 610, and one or more transmitters and/or receivers (TX/RX) 640 coupled to processors 610.

TX/RX 640 may be configured for bi-directional communication. TX/RX 640 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary to communicate with other network elements.

The processor 610 may be of any type suitable to the local technical network and may include, as non-limiting examples, one or more of the following: general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs), and processors based on a multi-core processor architecture. The device 600 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock that is synchronized to the master processor.

Memory 620 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 624, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact Disks (CD), digital Video Disks (DVD), and other magnetic and/or optical storage media. Examples of volatile memory include, but are not limited to, random Access Memory (RAM) 622 and other volatile memory that does not persist during power outages.

The computer program 630 includes computer-executable instructions that are executed by the associated processor 610. Program 630 may be stored in ROM 624. Processor 610 may perform any suitable actions and processes by loading program 630 into RAM 622.

Embodiments of the present disclosure may be implemented by means of program 630 such that device 600 may perform any of the processes of the present disclosure as discussed with reference to fig. 2-5. Embodiments of the present disclosure may also be implemented in hardware or a combination of software and hardware.

In some embodiments, program 630 may be tangibly embodied in a computer-readable medium that may be included in device 600 (such as in memory 620) or in another storage device accessible to device 600. Device 600 may load program 630 from a computer readable medium into RAM 622 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 7 shows an example of a computer readable medium 700 in the form of a CD or DVD. The computer readable medium has stored thereon the program 630.

Various embodiments of the disclosure may be implemented using hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the embodiments of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer executable instructions, such as instructions included in a program module, that are executed in a device on a target real or virtual processor to perform the methods 400 and 500 as described above with reference to fig. 4-5. Generally, program modules may include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions of program modules may be executed within local or distributed devices. In a distributed device, program modules may be located in both local and remote memory storage media.

Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable an apparatus, device or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are described in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. An apparatus, comprising:

At least one processor; and

At least one memory including computer program code;

The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to:

Determining, in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, a first estimate of a composite channel between the device and a second device, the plurality of first sensing signals being received from the second device via a second set of antennas and reflected by at least one object in the composite channel;

Determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatches for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from the first set of antennas and a transmit antenna from the second set of antennas;

determining compensation information for the composite channel based on the phase error information;

determining a second estimate for the composite channel based on the compensation information and the first estimate; and

Channel state information of the composite channel is transmitted to the second device based on the second estimate and the plurality of first sensing signals.

2. The apparatus of claim 1, wherein the first estimate comprises a phase error caused by the apparatus and the second apparatus, and the antenna pair phase mismatch comprises: a phase mismatch between a first phase of the first sense signal associated with a first one of the plurality of antenna pairs and a second phase of the respective first sense signal associated with each of the remaining ones of the plurality of antenna pairs.

3. The apparatus of claim 2, wherein the phase error information comprises a phase error matrix, and wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to determine the phase error information by:

Determining, for the time window, a set of phase mismatch coefficients indicative of a respective phase mismatch between the first antenna pair and each of the remaining antenna pairs from the plurality of antenna pairs; and

A phase error matrix is determined based on the set of phase mismatch coefficients.

4. The device of claim 1, wherein the first estimate of the composite channel comprises a first channel matrix determined based on a matrix of the composite channel, a first phase noise matrix associated with the device, and a second phase noise matrix associated with the second device.

5. The apparatus of claim 1, wherein the compensation information comprises a compensation matrix indicating antenna pair phase compensation corresponding to the antenna pair phase mismatch.

6. The apparatus of claim 5, wherein the first estimate of the composite channel comprises a first channel matrix of the composite channel and the second estimate of the composite channel comprises a second channel matrix of the composite channel, and wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to determine the second estimate by:

the second channel matrix is determined by multiplying elements of the same position in the first channel matrix and the compensation matrix.

7. The apparatus of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to:

in another time window, which is later than the time window, a second sensing signal is received from the second device, the second sensing signal being received from the second device based on a signal pattern determined from the channel state information.

8. The device of claim 1, wherein the device is a terminal device and the second device is a network device.

9. An apparatus, comprising:

At least one processor; and

At least one memory including computer program code;

Transmitting, via a second set of antennas, a plurality of first sensing signals to a first device having a first set of antennas within a time window, the plurality of first sensing signals reflected by at least one object in a composite channel;

Receiving channel state information of the composite channel from the first device, the channel state information being determined based on the plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from the first set of antennas and a transmitting antenna from the second set of antennas;

Determining a signal pattern based on the channel state information; and

In another time window, which is later than the time window, a second sensing signal is sent to the first device based on the signal pattern.

10. The apparatus of claim 9, wherein the antenna pair phase mismatch indicates: a phase mismatch between a first phase of the first sense signal associated with the first one of the plurality of antenna pairs and a second phase of the respective first sense signal associated with each of the remaining ones of the plurality of antenna pairs, and the compensation information indicates an antenna pair phase compensation corresponding to the antenna pair phase mismatch.

11. The apparatus of claim 9, wherein the at least one memory and computer program code are configured to, with the at least one processor, cause the apparatus to determine the signal pattern by:

Determining an estimate of the composite channel based on the CSI, the estimate for the composite channel being compensated by an antenna pair phase compensation corresponding to the antenna pair phase mismatch; and

Based on the estimate of the composite channel, the signal pattern is determined such that mutual information associated with the composite channel is maximized.

12. The device of claim 9, wherein the first device is a terminal device and the second device is a network device.

13. A method, comprising:

at a device, in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, determining a first estimate of a composite channel between the device and a second device, the plurality of first sensing signals being received from the second device via a second set of antennas and reflected by at least one object in the composite channel;

14. A method, comprising:

Transmitting, at the device, a plurality of first sensing signals to a first device having a first set of antennas via a second set of antennas within a time window, the plurality of first sensing signals reflected by at least one object in a composite channel;

Determining a signal pattern based on the channel state information; and

15. An apparatus, comprising:

Means for determining a first estimate of a composite channel between the apparatus and a second apparatus in response to receiving a plurality of first sensing signals via a first set of antennas within a time window, the plurality of first sensing signals being received from the second apparatus via a second set of antennas and reflected by at least one object in the composite channel;

Means for determining phase error information based on the first estimate, the phase error information indicating antenna pair phase mismatches for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receive antenna from the first set of antennas and a transmit antenna from the second set of antennas;

means for determining compensation information for the composite channel based on the phase error information;

Means for determining a second estimate for the composite channel based on the compensation information and the first estimate; and

Means for transmitting channel state information of the composite channel to the second apparatus based on the second estimate and the plurality of first sensing signals.

16. An apparatus, comprising:

Means for transmitting a plurality of first sensing signals to a first device having a first set of antennas via a second set of antennas within a time window, the plurality of first sensing signals being reflected by at least one object in a composite channel;

Means for receiving channel state information of the composite channel from the first apparatus, the channel state information being determined based on the plurality of first sensing signals and compensation information of the composite channel, the compensation information being determined based on antenna pair phase mismatch for a plurality of antenna pairs, the antenna pairs of the plurality of antenna pairs being different from each other and each antenna pair comprising a receiving antenna from the first set of antennas and a transmitting antenna from the second set of antennas;

means for determining a signal pattern based on the channel state information; and

Means for transmitting a second sensing signal to the first device based on the signal pattern in another time window that is later than the time window.

17. A computer readable medium comprising program instructions for causing an apparatus to perform at least the method of claim 13.

18. A computer readable medium comprising program instructions for causing an apparatus to perform at least the method of claim 14.